Effective legal systems glue together cohesive societies. Justice Harlan commanded that the implementation of a clear set of rules enables individuals “to settle their differences in an orderly predictable manner.” Without such a system, he added, “social organization and cohesion are virtually impossible...” The fundamental element of effective legal systems are the uniform application of its rules. Rules become unclear without consistency. In the early twentieth century, the American Bar Association displayed its appreciation of this societal model when it declared the need for a uniform set of procedural rules in the federal courts. The culmination of its effort, the enactment of the Federal Rules of Civil Procedure (“FRCP”), was consequently met with great approval. Today, Rule 23 of the FRCP presents a powerful tool: the class-action. The class-action device is a method of representative litigation that enables people to join together to adjudicate their claims. In turn, the consolidation of similar claims promotes efficiency, by preserving scarce judicial resources, and fairness, by ensuring consistent legal determinations. Indeed, fair and efficient outcomes will not result where members of proposed classes lack common interests. Likewise, proposed classes necessitate objective definitions for parties to discern who will be bound by potential judgements. Therefore, the uniform application of Rule 23(b)(3)’s predominance requirement, the former, and its implicit ascertainability requirement, the latter, help ensure Rule 23(b)(3)’s effectiveness. Ironically, courts have not uniformly utilized these standards when analyzing overbreadth — a major roadblock to class certification. Overbroad class definitions contain too many individuals with no legitimate claim for liability. While courts consistently deny certification for this manifestation, some do so through ascertainability analysis, while others do so under the predominance requirement. The lack of uniformity creates the prospect of unpredictability for litigants, irrespective of whether classes are certified. Claims under Rule 23 significantly impact our legal system and our economy. Inconsistent application of the rule’s requirements risks the potential for conflation of its standards, unnecessary litigation costs, and litigant forum-shopping. Therefore, courts must recognize this issue to promote analytic clarity.